In many chemical processes it is desirable to know the property of an emulsion, for example, in an alkylation process in a refinery, it is desirable to know the properties of the acid emulsion. In an alkylation process it is important to know the strength or settling time of the emulsion as well as the percentage of acid remaining in the system. The settling time is required to control the recycle rate of the acid while the quantity of acid determines the amount of make-up acid to be added to the process.
In the past, it has been customary to obtain a small sample of the alkylation emulsion in a sight glass and allow it to stand until the acid settles. By manually timing the settling and visually observing the percentage of acid on the emulsion, one obtained the necessary information. Based on these physical measurements, the alkylation process could then be adjusted to obtain optimum results. While this approach has been satisfactory in past operations, it is desirable to convert more of the process to automatic control. In order to obtain optimum results from any automatic control, it is necessary to have information on the physical properties of the emulsion.